The mechanism of hepatocellular necrosis, the basic event in viral hepatitis B, is unknown. Plasma membrane alterations may represent a fundamental process in the pathogenesis of hepatocellular injury. Therefore, it is our long-term objective to study antigenic plasma membrane changfes of hepatocytes infected with hepatitis B virus (HBV). We plan to test the hypotheses (1) that the expression of HBsAg on the cell surface is regulated and modulated by parameters such as cell cycle, antiviral antibodies, interferon and other factors and (2) that HBV infection results in an alteration of histocompatibility antigens on the plasma membrane. We will use two hepatocellular carcinoma cell lines (PLC/PRF/5 AND Hep 3B) which resemble hepatocytes and produce significant amounts of HBsAg, as the closest approximation to HBV infected hepatocytes currently available. Throughout the cell cycle and under the influence of modulating factors, we will quantitate HBsAg synthesis and secretion by radioimmunoassay or reverse hemagglutination in culture media and in disrupted cells, and on the cell surface by immunofluorescence and by saturation plateau radioimmunoassay. We will determine whether HBsAg forms an antigenic complex with histocompatibility antigens on the surface of cultured cells by co-capping experiments. These in vitro investigations will be supplemented by immunohistochemical studies of liver biopsy speciments of patients with hepatitis B for the expression of HBV and histocompatibility antigens. We will use both poly- and monoclonal antibodies. These studies may help to define the parameters that control and modulate HBsAg expression by HBV infected cells and the associated antigenic plasma membrane alterations. These changes may be related to immune lysis of hepatocytes and the mechanism of virus persistence in chronic liver disease. In addition, we may learn more about the effect of interferon and of antibody to HBsAg on HBV-infected cells. This is important in view of the use of interferon for treatment of chronic viral hepatitis B and because of vaccination trials now under way, for prevention of HBV infection.